The present invention relates to systems and methods for controlling the temperature and pressure of fluids.
Fluids such as gas, liquid, and mixtures thereof are used in many different applications. For example, fluids are used in chemical process systems, industrial process systems, and electrical generation systems. In order for such systems to operate, the system may require that the fluid have a predetermined temperature and pressure. For example, an electrical generation system that utilizes compressed gas to drive a turbine-generator may require the gas to have a predetermined temperature and pressure to maximize the operating efficiency of the turbine-generator.
Several automated and non-automated techniques have been employed to control temperature and pressure of fluids being used in such systems. However, these techniques have several shortfalls. For example, non-automated techniques are unable to maintain the temperature and pressure of fluids because of the stochastic nature of the system utilizing the fluid. That is, non-automated techniques are unable to take into account factors such as parasitic thermal capacitances, pressure swings, and mass flow and pressure demands, that affect the temperature and pressure of the fluid. Moreover, even if automated systems for controlling pressure and temperature are employed, their performance and applicability are often limited by one or more of the following factors:    (1) slow dynamic response;    (2) limited operating range and accuracy;    (3) maximum operating pressure limitations;    (4) excessive size; and    (5) excessive cost.Furthermore, attempts to compensate for changes in temperature and pressure result in an overshoot or undershoot in obtaining the desired temperature and pressure because the system may only be capable of making coarse adjustments.
Whether the temperature and pressure control techniques are automated or non-automated, such techniques typically use pressure regulators, flow control valves, or a combination thereof to implement temperature and pressure control. An electronic control system may be needed to operate pressure regulators and/or flow control valves in accordance with a temperature and pressure control technique. Such control systems may include devices specifically designed to control operation of a regulator, such as a dome loaded pressure regulator, by setting the setpoint pressure of the regulator. The setpoint pressure sets the pressure output of the regulator, minus a predetermined pressure drop caused by the internal mechanism of the regulator. These devices typically convert an electrical signal into an appropriately scaled pressure and include devices such as servo regulators, current to pneumatic (I/P) or voltage to pneumatic (E/P) transducers or converters. Thus, this appropriately scaled pressure may used to set the setpoint pressure of the pressure regulator.
However, these conventional electronic pressure control devices for setting the setpoint pressure are limited. For example, certain conventional control devices may be limited to providing maximum output pressures to 150 PSI and require a constant bleed to atmosphere during operation. A maximum output pressure of 150 PSI is limiting because the setpoint pressure may not be set to a pressure above 150 PSI. A constant bleed to atmosphere is undesirable because the source of such fluid may require constant replenishment. This can be costly or decrease operating efficiency. Other control devices may be capable of operating at pressures approaching 1000 PSI, but are susceptible to unsafe operating conditions, especially if the control system loses power. Another drawback of conventional pressure control devices is that many redundant or unnecessary electrical and mechanical components (e.g., digital-to-analog converters, pneumatics, etc.) are required to enable conventional pressure control systems to operate. This adds cost and decreases reliability.
In view of the foregoing, it is an object of the invention to provide improved systems and methods for controlling temperature and pressure of fluids.
It is also an object of the invention to provide a fluid routing system that rapidly and accurately changes the temperature of a fluid.
It is a further object of the invention to provide improved systems and method for accurately controlling the setpoint pressure being applied to a pressure regulator.
It is yet a further object of the invention to provide improved pressure control devices capable of providing failsafe operation, while limiting unnecessary leakage.